The invention relates to a wheel hub/constant velocity joint unit having a double-row bearing assembly arranged on the wheel hub and comprising at least one separate inner bearing ring pointing towards the constant velocity joint. The invention also covers wheel hub/constant velocity joint units comprising two inner bearing rings separated from and slid on to the wheel hub. In both cases, the outer bearing ring is undivided, as usual, and inserted directly into a wheel carrier.
As known in the state of the art, it is necessary for the two symmetrically arranged rows of bearings of the bearing assembly designed as angular contact deep groove bearings to be fitted with a pretension to ensure that, in view of the cyclic loads acting on the wheel, the bearings are play-free.
DE 36 18 139 A1 describes a unit of the above-mentioned type wherein an annular member is connected to the wheel hub by friction welding. The friction weld provides the pretension of the separate inner bearing ring at the joint end relative to the wheel hub. The inner bearing ring is completely embedded in the material of the wheel hub. In this embodiment, there are problems in accurately setting the pretension, as the pretension builds up by the friction weld that still flows after the friction welding operation. The dimensions of the friction weld change during the cooling process. As a result, the remaining pretension at the bearing assembly still changes at the end of the friction welding operation.
A non-rotating, form-fitting connection between the annular member and the outer joint part is achieved by inter-engaging end teeth which are tensioned by a bolted connection between the wheel hub and the outer joint member. Even with slight axial settlement symptoms, the connection is no longer play-free and is not suitable for the present unit.
From DE 36 08 346 A1 it is known to connect the outer joint part of a unit of the above-mentioned type directly with the wheel hub by friction welding. A collar of the outer joint part, is positioned radially outside tie friction weld, providing axial support between the outer joint part and the separate inner bearing ring at the joint end. Again, there are problems accurately setting the pretension because during the cooling process following the friction welding operation the axial dimension still changes. The remaining pretension at the bearing assembly hence changes at the end of the friction welding operation. The degree of change first has to be determined empirically, with the degree of scatter for welding operations being greater than for purely mechanical production process or cold-forming operations.
There is a further disadvantage in that the friction welding operation referred to has to be carried out before the constant velocity joint is finally assembled. The assembly procedure for the constant velocity joint thus must use a complete unitary constant velocity joint, wheel hub and bearing. This requirement complicates the procedure.
EP 0 610 782 A1 describes a unit of the type wherein the separate inner bearing ring at the joint end is axially tensioned on the wheel hub by a formed sleeve member. The sleeve member is integrally formed or slides on separately. Subsequently, the outer joint part typically is directly connected to the wheel hub by inter-engaging teeth and a securing ring.
With this embodiment, each time the wheel hub or bearing design is changed, the design of the outer joint part has to be adapted accordingly. This means that the manufacturer has to produce a large number of joint embodiments.
It is the object of the invention to provide a unit of the initially mentioned type wherein the method of tensioning the bearing assembly and the joint assembly procedure are improved.